The Function of the Secondary Oxygen Sensor?
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The secondary oxygen sensor, also known as the rear oxygen sensor, is responsible for detecting the oxygen concentration in the exhaust and sending feedback signals to the ECU. The ECU then adjusts the fuel injection volume of the injector to maintain the air-fuel ratio of the mixture near the theoretical value. The oxygen sensor in a car is a critical feedback sensor in the electronically controlled fuel injection system. It plays a key role in controlling vehicle exhaust emissions, reducing environmental pollution, and improving the combustion quality of the engine's fuel. Oxygen sensors are installed on the engine's exhaust pipe. If the oxygen sensor fails, the ECU of the electronic fuel injection system will not receive information about the oxygen concentration in the exhaust pipe, making it unable to perform feedback control on the air-fuel ratio. This can lead to increased fuel consumption and exhaust pollution, as well as engine issues such as unstable idling, misfires, and surging. Therefore, timely troubleshooting or replacement is essential. Cars are equipped with both front and rear oxygen sensors, which work in tandem. Below is an introduction to the front and rear oxygen sensors: 1. Front Oxygen Sensor: The front oxygen sensor typically has a 5-wire configuration. Its function is to provide feedback on the air-fuel ratio during engine operation. The optimal theoretical air-fuel ratio is 14.7:1. During operation, the engine injects fuel based on the calibrated MAP, striving to maintain the theoretical air-fuel ratio except under high load conditions. However, slight variations in fuel injection may occur during actual engine operation. In such cases, the engine can adjust the fuel injection volume based on the feedback from the front oxygen sensor to achieve the theoretical air-fuel ratio, thereby improving fuel efficiency and emission performance. 2. Rear Oxygen Sensor: The rear oxygen sensor typically has a 4-wire configuration and serves two purposes. First, it monitors the conversion efficiency of the catalytic converter to ensure that emissions do not fluctuate drastically. Second, it acts as a supplementary control for the front oxygen sensor in case the front sensor fails. Due to its operational characteristics, the rear sensor has minimal impact on short-term fuel injection adjustments but should be considered for long-term fuel injection corrections. The rear oxygen sensor is primarily used to monitor the conversion efficiency of the three-way catalytic converter, while the closed-loop control of the air-fuel ratio is managed by the front oxygen sensor. Therefore, as long as the front oxygen sensor is functioning properly, fuel consumption remains unaffected.
The secondary oxygen sensor, sometimes called the downstream oxygen sensor, is installed behind the catalytic converter in the exhaust pipe. Its role is to monitor the remaining oxygen levels in the exhaust gases, helping the vehicle's computer adjust the engine's air-fuel ratio to ensure more complete fuel combustion. Specifically, it checks the efficiency of the catalytic converter by comparing data with the primary sensor. If the difference between the two readings is too large, the catalytic converter may be failing, prompting the computer to optimize fuel injection or adjust timing to reduce emissions and improve fuel efficiency. With years of familiarity with this part, I know it may seem like a small component, but it plays a crucial role in meeting environmental certifications and passing annual inspections. When it fails, it triggers a warning light, significantly affecting driving. During city traffic jams, the sensor ensures smoother engine operation, extending overall lifespan. For repairs, using OEM parts is recommended to avoid compatibility issues.
